Neuroglial scar formation is considered to be a major impediment to regeneration in the mammalian central nervous system (CNS). In lower vertebrates, regeneration in the CNS is more successful, and glial cells appear to form a facilitative, rather than prohibitive, framework for axonal outgrowth. This proposal is designed to examine the cellular organization, population kinetics and membrane features characteristic of neuron-glial interactions in amphibians, fish and mammals. Comparative analyses of neuronal and glial activities will be focused upon species exhibiting different regenerative abilities but having neural tissue comprised of similar cellular elements. Observations made in these studies should identify essential structural elements upon which successful CNS regeneration is dependent.